TheAlgorithms-Python

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def wave(txt: str) -> list:
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    """
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    Returns a so called 'wave' of a given string
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    >>> wave('cat')
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    ['Cat', 'cAt', 'caT']
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    >>> wave('one')
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    ['One', 'oNe', 'onE']
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    >>> wave('book')
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    ['Book', 'bOok', 'boOk', 'booK']
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    """
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    return [
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        txt[:a] + txt[a].upper() + txt[a + 1 :]
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        for a in range(len(txt))
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        if txt[a].isalpha()
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    ]
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if __name__ == "__main__":
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    __import__("doctest").testmod()
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